Persistent positive scintigraphic evidence of disease after therapy predicts relapse in a number of studies.

Gallium scintigraphy and FDG-PET scan both have been shown to be useful in staging and following HD patients. However there is no definitive head-to-head comparison of the two modalities to establish if either is superior.

This study intends to directly compare FDG-PET to Gallium scintigraphy in the staging and follow up of newly diagnosed patients with HD.

Materials and Methods

36 HD patients were enrolled; median age 30, stage I-IV, only 3 with LPHD. 32 of 36 were treated with combined chemo-radiotherapy.

Each patient underwent FDG-PET and gallium scintigraphy prior to starting treatment. Follow up scans were done after 3 cycles of chemotherapy and after completion of all chemotherapy.

Two nuclear medicine physicians read all scans and were blinded to outcomes.

Results

5 patients had PET detected splenic disease not seen on gallium scan (p=0.05).

At completion of chemotherapy; Negative Predictive Value for relapse was 96% with PET and 90% with gallium; Positive Predictive Value was 50% for PET and 65% for gallium.

Sensitivity with PET was 80% vs. 40% with gallium. Specificity was 85% for PET vs. 96% for gallium.

Author's Conclusions

FDG-PET scanning is more sensitive than gallium in the setting of newly diagnosed HD.

PET is particularly well suited to detecting splenic disease.

Negative PET scan at the end of therapy predicts for a very favorable outcome.

Persistently positive PET at the completion of therapy is worrisome and warrants close follow up.

Clinical/Scientific Implications

Until the advent of FDG-PET scanning, gallium scanning was considered the standard for nuclear scintigraphic staging of HD. Though it has long been believed that FDG-PET is more sensitive than gallium, this study is among the first to provide data supporting that claim. This study is especially valuable in that all patients underwent both PET and gallium scan allowing direct comparisons between the two modalities. Though this study supports the replacement of gallium scan with PET in HD staging, one must not forget the higher false positive rate seen with PET scan. This may result in unnecessary patient anxiety and follow-up studies.

Oncolink's ASH Coverage made possible by an unrestricted Educational Grant from Ortho Biotech.